Enforcing software independent content protection in an electronic device during transcoding

ABSTRACT

A Set Top Box (STB) or client computer includes a communication interface operable to receive digital messages and digital content, memory, a transcoder, a central processing unit, and security processing circuitry. The security processor (or other components of the STB) is operable to identify protected digital content of the digital content that is to be isolated from the central processing unit during transcoding and to isolate the protected digital content from the central processing unit during the transcoding. The CPU may be denied access to a protected portion of the memory during the transcoding in which the transcoder stores non-scrambled protected digital content. The protected portion of the memory may be buffer memory accessible by the transcoder and not accessible by the central processing unit. The protected digital content may be identified from the digital message.

CROSS-REFERENCE TO PRIORITY APPLICATION

The present application claims priority to U.S. Provisional ApplicationNo. 61/449,370, filed Mar. 4, 2011, which is incorporated herein in itsentirety for all purposes.

BACKGROUND

1. Technical Field

The present invention relates generally to communication devices; andmore particularly to software security and content security serviced bythe communication devices.

2. Related Art

Communication systems are well known. Such communications includewireless networks, wired networks, satellite networks, and various othertypes of networks. These networks now currently support large volumes ofstreamed audio and video content. Such content is referred tohereinafter as one or more of video content, audio content, audio/videocontent, streamed content, digital content, streamed digital content.Such content may be streamed and then stored on an electronic device forlater presentation or simply presented upon receipt. All of such digitalcontent has ownership rights established therewith. In order for theowner of the digital content that is transmitted across one or morecommunication networks to be protected from authorized use, the digitalcontent is typically scrambled/encrypted/encoded or protected usinganother technique that precludes unauthorized use.

Currently existing networks in which audio and video content is commonlystreamed are cable modem networks, satellite service provider networks,wireless wide area networks, digital subscriber line networks, and othertypes of networks in which content is streamed from a service providerdevice or a server to a client device or an intermediate device. Serviceprovider networks typically include safeguards to preclude unauthorizedusers from intercepting and using content. The network operatorstypically load secure software to client devices, establish secure linksbetween server devices and client devices, and/or encrypted the digitalcontent so that it cannot be easily intercepted and copied. Further,these networks have heretofore been private, limited access, networks.However, the client devices of these networks, e.g., Set Top Boxes(STBs), are increasingly used to run applications that were previouslyreserved for Personal Computers (PCs). Currently STBs may be connectedto open networks such as the Internet. With past systems, the STBs wereoften closed systems that were protected by safeguards of the providernetwork including code signature authentication and other validationtechniques in systems.

With a central CPU of the STB having access to Internet content, thecentral CPU is vulnerable to attack by hacking, viruses, and othercontent that jeopardizes security STB. Typically, when a hacker accessesan STB, the hacker bypasses code updates and otherwise modifies the codethat is run by the STB. By having the code made vulnerable, the hackermay access streamed content received and processed by the STB. In thisfashion, the hacker may take the content and resell it for profit.Service providers have attempted to get around this problem by assigningcode versions to the various code downloads to the STB. However, hackersmay overcome this security measure by either blocking code updates or byspoofing the service provider devices into believing that the STB isrunning valid software.

These and other limitations and deficiencies associated with the relatedart may be more fully appreciated by those skilled in the art aftercomparing such related art with various aspects of the present inventionas set forth herein with reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram illustrating a communication systemimplementing one or more embodiments of the present invention;

FIG. 2 is a block diagram illustrating a STB constructed and operatedaccording to one or more embodiments of the present invention;

FIG. 3 is a flowchart illustrating operations according to one or moreembodiments of the present invention;

FIG. 4 is a block diagram illustrating the structure and operations ofone or more embodiments of the present invention;

FIG. 5 is a flowchart illustrating operations according to one or moreembodiments of the present invention;

FIG. 6 is a flowchart illustrating operations for content protectionaccording to one or more embodiments of the present invention;

FIG. 7 is a block diagram illustrating functionally the operations ofone or more embodiments of the present invention to protect digitalcontent upon receipt by an STB or client device;

FIG. 8 is a flowchart illustrating an operation according to anembodiment of the present invention for protecting digital contentduring transcoding;

FIG. 9A is a flowchart illustrating operations for protecting digitalcontent from the CPU during the transcoding process;

FIG. 9B is a flowchart illustrating operations of an STB or clientdevice in allocating protected memory for use in the transcoding processof the STB or client device;

FIG. 10 is a flowchart illustrating particular operations foridentifying content to be protected from access by a CPU duringtranscoding according to one or more embodiments of the presentinvention;

FIG. 11 is a block diagram illustrating the structure of a client deviceor STB that includes structure for protecting digital content duringtranscoding;

FIG. 12 is a block diagram illustrating another structure thatimplements one or more embodiments of the present invention;

FIG. 13 is a flow chart illustrating operations according to the presentinvention for securely carrying a code version message in a multi-stageencryption system; and

FIG. 14 is a block diagram illustrating further the operations of FIG.13 as enacted in one or more embodiments.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram illustrating a communication systemimplementing one or more embodiments of the present invention. Thesystem 100 of FIG. 1 includes a service provider device 102, which maybe a head end, a Set-Top Box (STB) 104, an Internet backbone 106, and aplurality of devices supported by the STB 104. The service providerdevice 102 may be one or more of a satellite communication system baseddevice, a wireless system supported device, or a media-based networksupported communication device. The media-based communication device maybe supported by a cable modem network, a telephone network supportingdigital subscriber line operations, an optical network, or another typeof network having media that couples communications from and to theservice provider device 102, or a combination of these. The serviceprovider device 102 may be referred to as a head end, a sever computer,a content server, a server provider computer, and/or interchangeablywith other descriptions thereof herein. The service provider device 102includes one or more receivers and decoders 124, one or more servercomponents 128, one or more digitized local video sources 130, softwareversion enforcement functionality 132, and content protectionenforcement functionality 134.

The service provider device 102 couples to the Internet backbone 106.The service provider device 102 may couple to the STB 104 via theInternet backbone 106. Further, the service provider device 102communicatively couples to the STB 104 via the type of communicationnetwork, e.g. satellite network, cable modem network, DSL network,optical network, wireless network of the particular service provider.The head end device 102 includes one or more of a satellite dish 136, anantenna 138, and a media interface 140 for coupling to its serviceprovider network. The service provider device 102 may stream content toSTB 104 and/or may provide Internet access to the STB 104. In streamingvideo and audio content to the STB 104, the service provider device 102of course desires that the digital content is protected via robustprotection techniques. Further, the service provider device 102 controlsthe software executed by the STB 104 and desires to have that softwarerobustly controlled to avoid hacking and interception of protected audioand video content.

The STB 104 includes software version enforcement functionality 142,content protection enforcement functionality 144, and various othercomponents that will be described further herein with reference to FIG.2. The STB 104 couples to one or more of a satellite dish 146, anantenna 148, and a media interface 150 to support communication with theservice provider device 102. The STB 104 services video system 108,Personal Video Recorder (PVR) 110, Personal Data Assistant (PDA) 112,pocket TV 114, television/media system 116, cell phone 118, watch 120,and digital computer 122. These devices 108, 110, 112, 114, 116, 118,120, and 122 may be supported wired or wirelessly depending upon theparticular embodiment hereof. In such case, the STB 104 providesInternet surfing functionality for each of these various devices108-122, streamed audio support for these devices, and/or streamed videosupport for these devices. The devices 108-122 may be supported within ahome, a business premises, or some other locale in which the devices108-122 reside.

The system 100 of FIG. 1 supports various operations according toembodiments of the present invention. According to a first embodiment ofthe present invention, the service provider device 102 and the STB 104cooperatively enforce software version robustness of the software uponthe STB 104. In such case, using the embodiments of the presentinvention, the service provider device 102 and STB 104 are able toverify that an appropriate and correct code version of software loadedand implemented by the STB 104 is employed. In such case, by insuringthat the appropriate software version STB 104 is employed, minimizationof risk of digital content and other downloaded content is supported.Likewise, the STB 104 and head end 102 cooperatively work to protectcontent that is streamed from the head end 102 to the STB 104. Thesevarious operations of the embodiments of the present invention will bedescribed herein with reference to FIGS. 3-5 herein

According to another aspect of the present invention, digital contentthat is downloaded to the STB 104 is only made available to a centralCPU of the STB 104 if in indicia that such content should be madeavailable is included with one or more messages received by the STB 104.In such case, the indications may be received in an ECM or anothermessage received by the STB 104 or client device. These principles andoperations will be described further with reference to FIGS. 6 and 7herein.

According to still another aspect of the present invention, a securityCPU of the STB 104 operates to preclude access by a central CPU toprotected data operated upon by a transcoder of the STB 104 during thetranscoding process. These aspects of the present invention will bedescribed with reference to FIGS. 8-11 herein. A central CPU 212 andsecurity CPU 214 of the STB 104 may operate in communication with oneanother to protect content that is downloaded to the STB from either theservice provider device 102 or another device communicatively coupled tothe STB 104.

A client/server implementation that embodies principles of the presentinvention is described herein with reference to FIG. 12. All principlesdescribed herein with reference to FIGS. 1-11 may be implemented by thestructure of FIG. 12.

A technique for receipt and processing of a multi-stage encrypted “codeversion message” according to one or more embodiments of the presentinvention is described further herein with reference to FIGS. 13 and 14.

FIG. 2 is a block diagram illustrating a STB constructed and operatedaccording to one or more embodiments of the present invention. The STB102 includes a service provider network interface 202 that couples toone or more of a satellite dish 146, an antenna 148, and/or media 150 tosupport communications between the STB 104 and the head end 102 and/orthe Internet backbone 106. For example, the STB 104 may receive Internetservice via the head end 102 or may have a separate interface to theInternet via one or more different connections. Likewise, the STB 102includes one or more wireless local area network (WLAN), wirelesspersonal area network (WPAN), and wireless wide area network (WWAN)interface 204. This interface 204 supports communications with one ormore WLAN/WPAN/WWANs with which the STB 104 communicates. Further, theSTB 104 includes a local area network (LAN)/wide area network (WAN)interface 206 that supports communications between the STB 104 and oneor more LANs or WANs.

The STB 104 further includes one or more user interfaces 208, a videooutput interface 210, a central CPU 212, a security CPU 214, memory 216,secure memory 218, video content buffers 220, and video processingcircuitry 222. The user interfaces 208 may include an interface to akeyboard, a mouse, a video display, or other types of devices thatallows the user to interface to the STB 104. For example, the STB 104may couple directly to an audio/video system including a monitor andaudio equipment. In such case, the STB 104 services streaming video fromthe head end 102 to one or more outputs serviced by the STB 104 via thevideo output I/F 210, the outputs being either directly coupled toaudio/video equipment or directly to one or more displays.

The central CPU 212 comprises one or more processing devices such as asystem processing unit, a digital signal processor, configurable logic,custom logic, an Application Specific Integrated Circuit (ASIC), DigitalSignal Processors (DSPs) or any other type of digital circuitry capableof processing computer software instructions and accessing the variouscomponents coupled thereto by a BUS. Security CPU 214 also includes oneor more processors, DSPs, or other devices capable of executing softwareinstructions and reading and writing to memory. Generally, the securityCPU 214 is for security operations and is does not run non-securesoftware programs, such as Internet Browsers and user programming, i.e.,the security CPU 214 is closely coupled by devices of a subscribernetwork.

Memory 216 includes one or more of DRAM, SRAM, ROM, PROM, opticalmemory, magnetic memory, flash memory, or any other type of memorycapable of storing computer software instructions and/or data andproviding access thereto. The memory, in some embodiments, includes bothvolatile memory and non-volatile memory. Typically, a code version andother reference data would be stored in non-volatile memory, so that itwould remain intact during power down. Secure memory 218 has a similarstructure to memory 216 but may have its access limited by security CPU214. Video content buffers 220 serve to store video content as it isreceived or transmitted by the STB 104. Video processing circuitryincludes one or more components that are operable to demultiplex,decrypt, decode, transcode, encode, encrypt, and/or multiplex streamedvideo and/or audio content.

According to another aspect of the present invention, digital contentthat is downloaded to the STB 104 is only made available to the centralCPU 212 if in indicia that such content should be made available isincluded with one or more messages received by the STB 104. In suchcase, the indications may be received in an ECM or another messagereceived by the STB 104 or client device, or any message conveyed by thehead-end which also transmits keys. By tying the code version and/orcontent access rights to the key delivery system, embodiments of thepresent invention ensure that any attempt to bypass head end 102commands will result in an inability to decrypt content.

The teachings of the present invention may also be applied to devicessuch as CableCards, which may receive information from the head end 102which is tied to Copy Protection (CP) key exchange with the STB 104 viaa secure channel. These teachings may also be applied to IP deliverysystems, which transmit keys via secure messages. These principles andoperations will be described further with reference to FIGS. 6 and 7herein as examples.

According to another aspect of the present invention, digital contentthat is downloaded to the STB 104 is only made available to the centralCPU 212 if an indicia that such content should be made available isincluded with one or more messages received by the STB 104. In suchcase, the indications may be received within the encrypted contentstream as a special supplemental message, e.g. elementary stream userdata in MPEG-2 video, or Supplemental enhancement information (SEI)message in H.264 video, received by the STB 104 or client device. Acontent descrambler may securely decrypt this special code versionmessage and store it in a secure register or memory, which can only beaccessed by the security CPU 214. To ensure the robustness of themechanism, this message may always be inserted in the critical codingstructure of the content, e.g. along with the video sequence header,I-picture header, etc. The secure register or memory only updates thechange of the code version message. These teachings will be discussedfurther with reference to FIGS. 13 and 14. As is shown in these FIGS.,content is segmented into blocks for encryption. A code version messageis inserted in such a way that, for each stage of encryption/scrambling,a part of the code version message will be always encrypted togetheralong with the content in one encrypted block. This ensures that anyattempt to bypass the code version message will make the contentundecodable. This also enables multi-stage transcryption to supportsecure code version updates.

According to another aspect of the present invention, the security CPU214 operates to preclude access by the central CPU 212 to protected dataoperated upon by a transcoder of the video processing circuitry 222during the transcoding process. These aspects of the present inventionwill be described with reference to FIGS. 8-11 herein. According to yetanother aspect of the present invention, the central CPU 212 andsecurity CPU 214 of the STB 104 operate in communication with oneanother to protect content that is downloaded to the STB from either theservice provider device 102 or another device communicatively coupled tothe STB 104.

FIG. 3 is a flowchart illustrating operations according to one or moreembodiments of the present invention. The operations 300 of FIG. 3 areperformed by the STB 104 in cooperation with the service provider device102 of FIG. 1. With another implementation, the operations 300 of FIG. 3are performed by the system 1200 of FIG. 12. The operations 300 of FIG.3 serve to guarantee or determine whether or not valid softwareinstructions exist on the STB 104 (or other client device).

Operations 300 commence with the STB receiving a digital message from aremote device that includes a rights portion and a key portion (step302). The remote device may be the head end 102 of FIG. 1 or anotherserver-type device. The structure of the digital message is describedfurther with reference to FIG. 4. With the embodiment of FIG. 4 inparticular, the digital message includes a key portion that relates tothe decryption of streamed audio and/or video content received from theSTB. The rights portion is a portion of the digital message that issubsequently used to validate software that is stored on the STB. Withother embodiments, the rights portion relates to the decryption of othertypes of data transmitted to the client device.

Operation 300 continues with the STB extracting a key portion from thedigital message (step 304). Then operation continues with the STBextracting a rights portion from the digital message (step 306). Thedigital message may be an Entitlement Control Message (ECM) that thehead end 102 sends to the STB 104. Some systems may not use ECMs. InCableCard systems, the digital message may be sent by the head-endembedded in the encrypted data, then extracted by the CableCard, andconveyed to the STB 104 using a secure channel at the same time as theCP key. This conveyance to the STB 104 would be seamless, such thatinterfering with the rights sent to the STB 104 would also prevent theCP key from being loaded. In IP delivery systems, the rights field mayalso be tightly encrypted with the content decryption key, to protect itin the same manner as for CA. The teachings of the present invention maybe applied to all content and key delivery mechanisms, regardless of thesource or delivery method of the content.

The digital message may be routed within the STB 104 via a smart card,via CableCard using secure channel, or by any other means to thesecurity processor 214 previously described with reference to FIG. 2.Conventional ECMs include a key, which is later used for contentdecoding purposes. According to the present invention, a rights field isadded to the ECM or other message sent from the head end 102 to the STB104. This rights field is added in such a way that the key and therights are inseparable in the encrypted domain, such that interferingwith the delivery of the rights field to the security processor willalso interfere with the key delivery.

Operation 300 continues with the STB decrypting the key portion of thedigital message (step 308). Then, operation 300 includes the STBdecrypting the rights portion of the digital message (step 310). As willbe further described with reference to FIG. 4, the rights portion may beencrypted based upon the key portion. Operation 300 continues with theSTB validating the rights portion of the digital message (step 312).When the rights portion arrives in an encrypted format, the STB firstdecrypts the rights portion 310 and then validates the rights portion atstep 312 based upon its contents.

Operation 300 continues with the security processor or logic of the STBextracting a code version from the rights portion of the digital message(step 314). The security processor or logic then compares the codeversion to the stored code version that was stored in a secure memorywithin the STB (step 316). Based upon the operation of step 316, thesecurity processor or logic determines whether or not the code versionof the code implemented on the STB is accurate. Upon a favorablecomparison, the comparison at step 316 results in a pass action (step320). In such case, when the code version is validated at step 316,normal operations of the STB are enabled for subsequent processing ofprogramming streamed to the STB 104 from the head end.

Upon a failure action at step 318 as determined based upon thecomparison of the code version to the stored code version at step 316,the STB executes an error action. This error action may be sending amessage to the head end 102 (or other service provider device) forsoftware instruction reloading to the STB. Other interactions mayinclude rebooting the STB and/or disabling the decryption of digitalcontent of the STB. In such case, by having the unfavorable comparisonof the stored code version to the code version determined from thedigital message, the STB may be operated to protect content streamedthereto.

As will be described further with reference to FIG. 4, the rightsportion of the digital message may include an integrity portion and thecode version. The integrity portion may be a known constant that hasbeen used to form a segment of the rights portion and other fields thatthe STB uses to validate that the rights portion of the digital messageis accurate and may support the subsequent operations 300 of FIG. 3. Theintegrity portion may also involve any combination of digest andsignature over the key/rights delivery message that will be apparent toone of ordinary skill in the art.

FIG. 4 is a block diagram illustrating the structure and operations ofone or more embodiments of the present invention. Streamed content 400is received by the STB. The streamed content includes transport packets(XPT PKTs) and the ECMs or other key delivery messages. As isillustrated, the streamed content 400 includes XPT PKTs that areinterspersed with the ECMs. Upon receipt of an ECM, the ECM is dividedinto the rights portion and the key portion at 402. The key portion isthen decrypted with operation 408 based upon a program key that isproduced by n-1 previous key ladder stages functionality 404. Thedecryption operation uses the program key 406 to decrypt the key portionof the ECM 402 at operation 408. Produced by the decryption operationstep 408 is a program identification (PID) key 410. With the embodimentof FIG. 4, the PID key 410 is used to decrypt the rights portion of theECM 402 via decryption operation 412. These operations may also beapplied to a system in which data arrives in non-transport streamformat, such as may occur over an IP delivery system with other embeddedkey messages.

With the embodiment of FIG. 4, the rights field of the ECM 402 may be aseparately encrypted field. For example, with the key portion encryptedusing AES, the key portion of the ECM 402 is 128 bits wide, which is anative AES block size. The rights portion of the ECM 402 uses up asecond 128 bit word. However, because the rights field is in aseparately encrypted field from the key portion, it may be possible fora hacker to remove part of the ECM 402 (the rights field) and replace itwith a rights field from a previous ECM, while still retaining the keyportion of the ECM 402. Doing this results in bypassing securityprotection and allowing a previous code version to be assumed.

According to another aspect of the present invention, the head end 102encrypts the rights portion of the ECM 402 using an ECM key. The STB 104then decrypts the key portion according to the operations of FIG. 4.With the decryption performed at step 412, what is produced is adecrypted rights portion 414. The decrypted rights portion includes aknown constant, other fields, and a code version. The known constant iscompared to a previously determined known constant to first validate therights portion of the ECM 402. Then, with the decrypted rights portion414 validated, security processor 214 compares the code version of thedecrypted rights portion of the ECM 402 with a code version extractedfrom memory 416. The security processor 214, after making thiscomparison, then initiates either recovery operations or successfulcomparison operations to support further operations of the STB.

According to another aspect of the present invention, Cipher-BlockChaining (CBC) or any other cross-word chaining may be used to tie thekey portion to the rights portion. For example, the key delivery messagemay be encrypted with AES-CBC across both the key and the rightsportion/words. Then, substituting the rights portion of one key messagewith that of another key message will break the chain, and will resultin unusable keys. By doing so, interception and attempted replacement ofthe rights portion will cause the key to be unusable to decode content.

FIG. 5 is a flowchart illustrating operations according to one or moreembodiments of the present invention. Operations of an STB having acentral processor and a security processor are illustrated. However,with other embodiments, the operations of FIG. 5 may be performed by aclient computer interacting with a server computer. With the embodiment500 of FIG. 5, a security processor 214 controls or limits the operationof a central CPU 212, as was illustrated in FIG. 2. Operation commencesat start up, reboot, or power up. In a first operation, after restart,reboot, or power up, the security processor disables a function of thecentral processor (step 502). This function disablement includesprecluding the ability of the STB to decode or otherwise processprotected digital content.

Operation continues with the security processor generating andencrypting a random number (step 504). The security processor theninitiates transmission of the encrypted random number to a serviceprovider device such as the head end 102 (step 506). The securityprocessor then waits and receives a response message from the head end(at step 508). The security processor then decrypts the response message(step 510). The STB then validates the decrypted response message (step512). Validating the encrypted response message may include multiplemethods such as signature, digest comparison, and other methods known tothose skilled in the art.

Then, with the response message validated, the security processorextracts a code version from the rights portion (step 514). The securityprocessor then compares the code version of the extracted version fromthe response message to a stored code version (step 516). Upon afavorable comparison, the security processor will execute a pass action(step 520). If the comparison at step 516 was unfavorable, the securityprocessor executes a fail action (step 518). As was the case with theoperations of FIG. 3, a pass action includes fully enabling the centralCPU to perform decoding and decryption of streamed content for storageand/or presentation to a user. An error action as implemented at step518 may include sending a message to a service provider to initiatesoftware instruction reloading to the STB.

FIG. 6 is a flowchart illustrating operations for content protectionaccording to one or more embodiments of the present invention. Theoperations 600 of FIG. 6 may be performed by the STB 104 in cooperationwith the service provider device 102 of FIG. 1. Likewise, the operations600 of FIG. 6 may be performed by a client device that is incommunication with a server device. Such combination is subsequentlydescribed herein with reference to FIG. 12. The operations 600 of FIG. 6may be performed by other devices as well without departing from thescope and spirit of the present invention.

The operations 600 of FIG. 6 commence with the STB receiving a digitalmessage from a remote device, the digital message including a rightsportion and a key portion (step 602). A security processor or logic ofthe STB then extracts the key portion from the digital message (step604). Next, the security processor or logic extracts a rights portionfrom the digital message (step 606). The digital message described withreference to FIG. 6 may be an ECM as was previously described hereinwith reference to FIG. 4, or may be any message that conveys contentdelivery keys to the STB.

Operations 600 of FIG. 6 continue with the security processor or logicdecrypting the key portion of the digital message (step 608). Indecrypting the key portion at step 608, the security processor or logicuses a decryption scheme that is consistent with the encryption schemeused by the head end or server that created the digital message. Oneexample of such a decryption scheme will be described herein withreference to FIG. 7. The security processor or logic then decrypts therights portion (step 610). Resultantly, after executing steps 602-610,the security processor or logic has generated a key portion that may besubsequently used to descramble content provided to the STB from thehead end or other remote device. Further, the security processor orlogic has also generated a key portion that may be subsequently used toprotect portions of the digital content that is received by the STB.

Next, the security processor or logic validates the rights portion (step612). With the operations of step 612, the security processor or logicuses additional steps to ensure that the rights portion of the digitalmessage is valid and will correctly serve to be used to right protectdigital content as it is received by the STB. The security processor orlogic then extracts program ID protect data from the rights portion ofthe digital message (step 614). While FIG. 6 refers to program IDprotect data, the terminology content identifier or content identifiersmay be used herein. As the reader will appreciate, content received bythe STB may be segments of a larger content group. For example, thecontent may include a plurality of streams of video and/or audio data.Further, the content may be one or more data files being downloaded tothe STB, a software program, or another type of data being downloaded tothe STB. This data will be divided into smaller groups of data that willbe transmitted to the STB in data segments. These data segments may beidentified to belong to a larger group of data. According to embodimentsof the present invention, each of these data segments may haveassociated therewith a content identifier. The content identifier may bea Program ID, File ID, data group ID, or another identifier, whichidentifies the incoming data as associated with a particular ID.Depending upon the ID of the content, operations according to thepresent invention will either protect or not protect the content fromthe central CPU. The operations 600 of FIG. 6 apply to identifiedcontent, independent of its content type.

In one particular operation of the STB according to the method 600 ofFIG. 6, the STB receives digital messages and digital content. Thedigital messages, when processed according to steps 602-614, produceprotection data for at least some PIDs of programming received by theSTB. The protection data is an indicator of whether the decryptedcontent belonging to each PID (or protected stream or other receiveddata, i.e., IP data) should be allowed into host CPU accessible area.For example, as will be subsequently described with reference to FIG. 7,the STB may be operable to receive and descramble a plurality ofaudio/video streams from the head end 102. Each of these audio/videostreams has an associated PID or other stream designator therewith.Based upon the PID or other stream designator, and the rights fieldassociated with the key, the STB is operable to uniquely process each ofthe audio/video streams. Thus, at step 616, the STB is operable todetermine protection data for at least some of a plurality ofaudio/video streams received by the STB. Of course, the STB may onlyreceive a single audio/video stream and will process that singleaudio/video stream according to the protection data corresponding to theparticular program ID.

For each audio/video stream received by the STB, upon determining thatthe audio/video stream is not protected, the STB will write theunprotected data to unprotected memory (step 618). Further, for eachprogram ID/PID associated with an audio/video stream that is rightprotected, the STB will write the protected data to a protected portionof memory (step 620). In one particular operation, the STB will scramblethe protected data prior to writing the protected data to the protectedportion of the memory.

Subsequent to the operations 600 of FIG. 6, the STB may allow access tothe protected portion of the memory only to audio/video processingresources of the STB and deny access to the protected portion of thememory to the central CPU 212 of the STB 104. In such case, the STB 104includes hardware, e.g., security processor, and/or software safeguardsto limit access to memory to the various processing resources within theSTB.

As was the case with the embodiment of FIG. 4, the rights portion of thedigital message may include a validation portion that the securityprocessor or logic of the STB 104 uses to validate the rights portion.This validation portion may include a known constant and/or other fieldsthat verify that the rights portion of the digital message is in factvalid and should serve to support the operations of the presentinvention. Other methods of validation will be apparent to those skilledin the art.

FIG. 7 is a block diagram illustrating functionally the operations ofone or more embodiments of the present invention to protect digitalcontent upon receipt by an STB or client device. A Conditional Access(CA) digital stream 700 is received by the STB, which includesinterspersed digital content (XPT PKTs) and digital messages (ECMs),which is transmitted by a head end 102 or server computer. The STB orclient device extracts the digital messages from the streamed contentand produces the digital message 702, which includes a key portion and arights portion. The digital content of the streamed structure 700 isconditional access (CA) audio/video content that is generally knownwithin the audio/video art.

The ECM 702 includes a key portion, which is decrypted by functionaldecryption blocks 708 using a program key 706 that was produced by a keyladder stages functional device 704. The decrypted key portion isdecrypted by a functional block 708 to produce a PID key 710. The PIDkey 710 is used by functional decryption block 712 to produce adecrypted rights portion 714. The decrypted rights portion 714 includesone or more PID protect data IDs or bits corresponding to one or morestreams of digital content received by the STB. Each of the streams ofthe digital content includes a corresponding PID.

The PID key 710 is also used by functional block 716 for CA descramblingof a plurality of audio/video streams. Based upon the one or moreprotection bits of the decrypted rights portion 714, the STB streams thedigital content into either unprotected memory 718 or protected memory720. With the example of FIG. 7, program IDs “A” and “B” are unprotectedwith their protection bit equal to “0”, while the streamed contentrelating to program ID “C” is protected with its protection bit set to“1”. In such case, the audio/video streams corresponding to program IDs“A” and “B” may be streamed to either the unprotected memory 718 or theprotected memory 720 for subsequent access by the central CPU 212, thesecurity CPU 214, and/or video processing circuitry 222 of the STB 104of FIG. 2.

Because the audio/video stream having the program ID “C” has aprotection bit equal to “1”, the digital content corresponding to theprogram ID “C” stream is only written to protected memory 720 forsubsequent access only by resources of the STB 104 other than thecentral CPU. In some embodiments, the protected memory 720 may only beaccessed by video processing circuitry 222 of the STB 104 of FIG. 2. Inother embodiments, other components of the STB may also access theprotected memory 720. Further, as was previously described, according toone embodiment of the present invention, the digital contentcorresponding to the program ID “C” may be scrambled prior to itswriting to the protected memory 720. Further, in another embodiment,digital content corresponding to PID “A” and PID “B” are only written tothe unprotected memory 718 and the digital content corresponding to PID“C” is only written to protected memory 720. The optional writingillustrated in FIG. 7 is shown to indicate that unprotected content maybe written anywhere in the memory while protected content can only bewritten to that portion of memory 720 that is not accessible by thecentral CPU 212 of the STB.

FIG. 8 is a flowchart illustrating an operation according to anembodiment of the present invention for protecting digital contentduring transcoding. The operations 800 of FIG. 8 begin with a STB orclient device receiving a digital message and digital content from aremote device (step 802). According to one embodiment of the presentinvention as was described previously herein with reference to FIG. 1,the receiving device is an STB 104 and the transmitting device is a headend 102. According to an embodiment that will be described furtherherein with reference to FIG. 12, the transmitting device is a server1202 and the receiving device is a client 1204. Each of the server 1202and the client 1204 is a digital computer that is coupled to theInternet.

Referring particularly to FIG. 8, the receiving device is operable tostore the digital message and the digital content in memory (step 804).A security processor, for example, of the receiving device thenidentifies protected digital content that is to be isolated from acentral processing unit during transcoding (step 806). As will bedescribed further herein with reference to FIGS. 9-11, the transcoder isa component of a client computer or STB. The digital content is receivedby the device in a scrambled format, according to an H.264, MPEG, AVG,or another encoding or encryption standard. The scrambled content isthen retrieved from memory by a transcoder of the device (step 808).When retrieved from memory, the digital content is still in itsscrambled format. However, when transcoding of the digital content bythe transcoder (step 810), the digital content is first descrambledprior to transcoding. Thus, during the transcoding process digitalcontent is in an unprotected format which could be accessed by the CPUand intercepted in that format.

Thus, according to the present invention, the protected digital contentthat was identified in step 806 is isolated during transcoding from theCPU (step 812). The manner in which the protected digital content isisolated from the CPU at step 812 may take differing forms according tovarious embodiments of the present invention. According to a firstembodiment, a security processor 214 precludes access of those portionsof memory in which the descrambled content is stored by the transcoderduring the transcoding process. In another embodiment, the transcoderitself is controlled to preclude writing the digital content in itsunscrambled format into those portions of memory that are accessible bythe CPU. For example, the transcoder may use secured buffers to storethe digital data in its descrambled format during the transcodingprocess. These secure buffers are not accessible by the CPU. Further, adirect memory access (DMA) engine of the transcoder may be operated suchthat the digital content during transcoding in its unscrambled format isnot stored in memory accessible to the CPU. In other embodiments, otherdata movement engines within the transcoder are protected from centralCPU access, so that they cannot be used to move data from secure andnon-secure regions.

According to another aspect of the present invention, the output of thetranscoder is forced to go to secure buffers by a security processor orhardware, where such security buffers cannot be read by the CPU. Stillfurther, transcoder output buffers are only accessible by hardwareengines or local CPUs other than the central CPU to keep the unprotecteddigital content from the central CPU access. Still further, the cleartranscoded data prior to rescrambling is forced to be rescrambled by thetranscoder during the transcoding process when written to memory. Eventhough this embodiment will require multiple steps for scrambling anddescrambling during the transcoder process it would protect the digitalcontent during the transcoding process from interception by the CPU.

FIG. 9A is a flowchart illustrating operations for protecting digitalcontent from the CPU during the transcoding process. The operations 900of FIG. 9A begin with a security processor or other logic of the STB 104or client device determining a protected portion of memory in which thetranscoder stores non-scrambled data during transcoding (step 902).Then, the security processor or other logic of the STB precludes accessby the CPU to the protected portion of the memory during transcoding(step 904).

FIG. 9B is a flowchart illustrating operations of an STB or clientdevice in allocating protected memory for use in the transcoding processof the STB or client device. Operations 950 commence with a securityprocessor or other logic of the STB or client device allocatingprotected buffers in which the transcoder stores non-scrambled dataduring the transcoding process (step 952). Then, operation continueswith the security processor or other client or STB device precluding thecentral processing unit access to the protected buffers duringtranscoding (step 954).

FIG. 10 is a flowchart illustrating particular operations foridentifying content to be protected from access by a CPU duringtranscoding according to one or more embodiments of the presentinvention. The operations 1000 of FIG. 10 commence with the STB orclient device receiving a digital message from a remote device thatincludes a rights portion and a key portion (step 1002). The STB thenextracts a key portion from the digital message (step 1004). The STBthen extracts a rights portion from the digital message (step 1006). Theoperations of FIG. 10 are described in part in the block diagrams ofFIGS. 4 and 7, however with particular applicability to determining oridentifying protected content.

The STB or client device then decrypts the key portion of the digitalmessage (step 1008). Then, the STB decrypts the rights portion of thedigital message (step 1010). In one particular aspect of the presentinvention, the decrypted key portion may be required to decrypt therights portion. In such case, the operation of step 1008 is used todecrypt a key portion and produce a decrypted result. Then, the rightsportion is decrypted using the decrypted result to produce the decryptedrights portion.

Then, the rights portion is optionally validated based upon its content.Referring to FIGS. 4 and 7, the decrypted rights portion may include aknown constant or other validation field that is used to validate therights portion at step 1012. After validation, the rights portion maythen be used to extract protection data regarding the digital contentreceived by the STB or client device (step 1014). In one particularembodiment, a plurality of programs, each with a particular PID, isreceived by the STB or client device for processing. Further, in therights portion, there is a plurality of corresponding protection bits ordata that corresponds to the plurality of PIDs of the digital content.In such case, then each of the PIDs operated upon by the STB or clientdevice have a corresponding protection indication via a protection bitor other data. Finally, based upon the information received in therights portion of the digital message, the security processor or otherdevice precludes access to protected PID digital content by the centralprocessing unit during transcoding by the transcoder (step 1016). Fromstep 1016 operation concludes.

FIG. 11 is a block diagram illustrating the structure of a client deviceor STB that includes structure for protecting digital content duringtranscoding. The structure 1100 of FIG. 11 includes the central CPU 212,security CPU 214 and a plurality of other components used during thetranscoding process as well as during other operations of the device.Digital content is received by transport demux 1102 which separates thetransport stream (CA Stream) into a plurality of program streams. Thisoutput of the transport demux 1102 is written to compressed data buffer1104. The compressed data buffer 1104 stores the digital content as itis received in a scrambled format that is not susceptible to piracy orother unauthorized access by the central CPU 212.

The transcoder 1106 performs transcoding of the streamed digitalprogramming that is stored in the compressed data buffer 1104.Operations of transcoder 1106 may be tailored to a particular clientdevice serviced by the STB or client computer prior to theirpresentation. For example, the transcoder 1106 may receive programmingin an HD format as supported by H.264 that is not needed by a pocket TV114 or PDA 112 that was previously described with reference to FIG. 1.In such case, the transcoder 1106 alters the digital content so that itmay be better displayed by such rendering device (TV 114 or PDA 112) ormore easily transported thereto with lesser data transport requirements.

Transcoder 1106 includes a decoder 1108 that decodes the digital data.The output of the decoder 1108 is written to a decompressed data buffer1110. The decompressed data buffer 1110 may store digital content in anunprotected format that is to be precluded from access by the centralCPU 212. Direct memory access (DMA) engine 1114 couples to thedecompressed data buffer 1110 and other secure buffers 1112. In someoperations, the central CPU 212 may have access to the DMA 1114.However, when digital content has been determined to be protected, thesecurity CPU 214 of FIG. 11 will preclude the central CPU from accessingthe DMA 1114. Further, other buffers 1128 coupled to the transcoder 1106that store content in an unprotected format are protected by thesecurity CPU 214 from access by the central CPU 212.

Transcoder 1106 includes encoder 1107 that includes the DMA 1114,multiple sub-clients 1116 and output clients 1118. The multiplesub-clients 1116 and output clients 1118 may include a plurality ofdiffering functioning devices that are employed in the transcodingprocess. The output of the transcoder 1106 is written to compressed databuffer 1120. The data is read from the compressed data buffer 1120 byhardware read engine 1122. The hardware read engine 1122 produces outputthat is received by encryption engine 1124 that encrypts the data andwrites the data to other buffers 1126. The output of the encoder 1107may also be written to the other buffers 1128, which are protected bythe security processor from the central CPU 212 when storing protecteddata.

According to another aspect of the present invention, the transcoder1106 operates on a plurality of programs each of which has a uniqueprogram ID (PID). In such case, the central CPU 212 may have access tothe unprotected digital content during transcoding by the transcoder1106 but may be precluded from access to the transcoder 1106 forprotected digital content. Thus, the security CPU 214 of FIG. 11 willonly precludes access by the central CPU 212 for the transcoding ofprotected digital content but not unprotected digital content.

According to other operations, the security processor 214 is operable toprotect both the transcoder input and the transcoder output from thecentral processing unit 212. Further, the security processor 214 may beoperable to protect at least some of a plurality of buffers 1110, 1112of the transcoder 1106 from the central processing unit 212 duringtranscoding. In still other operations the security processor 214 isoperable to cause the transcoder 1106 to use memory having particularaddresses for storage of intermediate content during transcoding. Thesecurity processor 214 may be operable to limit access of the centralprocessor 212 to buffers used by the transcoder 1106 for storage ofintermediate transcoding content. The DMA engine 1114 may be operable toencrypt transcoder output before the data is output from a protectedportion of memory. In such case, the DMA engine 1114 is under control ofthe security CPU 214.

FIG. 12 is a block diagram illustrating another structure thatimplements one or more embodiments of the present invention. Thestructure of FIG. 12 includes a server computer 1202 and a clientcomputer 1204 that are coupled by the Internet 1203 or another network.The server computer 1202 includes server computer components 1206,software version enforcement functionality 1208, and content protectionenforcement functionality 1210. The software version enforcementfunctionality 1208 and content protection enforcement functionality 1210were previously described herein and may be implemented by the structure1200 of FIG. 12.

Client computer 1204 includes client components 1212, software versionenforcement functionality 1214 and content protection enforcementfunctionality 1216. The software version enforcement functionally 1214and content protection enforcement functionality 1216 perform functionspreviously described herein and employs structures previously describedherein with reference to FIGS. 1-11. Thus, the structure 1200 of FIG. 12may be performed in any of the various operations previously describedherein with reference to FIG. 11 and incorporates structures previouslydescribed herein with reference to FIG. 11 to embody the teachings ofthe present invention.

FIG. 13 is a flow chart illustrating operations according to the presentinvention for securely carrying a code version message in a multi-stageencryption system. The operations 1300 of FIG. 13 are performed by theSTB 104 of FIG. 1, by the client computer 1204 of FIG. 12 or by anothercomputing device that receives remote content and whose code versionsare tracked by another computing device. The operations 1300 of FIG. 13serve to guarantee or determine whether or not valid softwareinstructions exist on the STB 104 (or other client device 1204).

Operations 1300 commence with the STB receiving digital data from aremote device, the digital data including encrypted content and amulti-stage encrypted code version message (step 1302). The remotedevice may be the head end 102 of FIG. 1 or another server-type devicesuch as the server computer 1202 of FIG. 12. The structure of thedigital data and its flow according to the operations 1300 of FIG. 13are described further with reference to FIG. 14. The encrypted contentmay be streamed audio data, streamed video data, software, bulk data, oranother type of data intended for the STB 104 or client computer 1204.

Operations 1300 continue with a security processor or other logicdecrypting the digital data using a first decryption technique, e.g.,AES-CBC, to produce decrypted content and an encrypted code versionmessage (Step 1304). Because the code version message was multi-stageencrypted, after its first stage decryption, the code version message isstill encrypted according to its second stage encryption format.Operation continues with the security processor or other logicdecrypting the encrypted code version message using a second decryptiontechnique, e.g., AES-CTR to produce the code version message in adecrypted format (step 1306). The code version message is stored in asecure register by the security processor or logic so that it cannot beaccessed by the CPU. The code version message may be routed within theSTB 104 via a smart card, via CableCard using secure channel, or by anyother means to the security processor 214 previously described withreference to FIG. 2.

Operations 1300 continue with the security processor or logic processingthe code version message to determine a reference code version (step1308). The operations of step 1308 may include validating the codeversion message based upon its contents using a technique same/similaras that describe with reference to the prior FIGS.

Operations 1300 continue with the security processor or logic of the STBcomparing the reference code version to a stored code version that wasstored in a secure memory within the STB (step 1310). Based upon theoperation of step 1310, the security processor or logic determineswhether or not the code version of the code implemented on the STB isaccurate. Upon a favorable comparison, the comparison at step 1310results in a pass action (step 1314). In such case, when the codeversion is validated at step 1310, normal operations of the STB areenabled for subsequent processing of programming streamed to the STB 104from the head end. Upon a failure action at step 1312 as determinedbased upon the comparison of the reference code version to the storedcode version at step 1310, the STB executes an error action. This erroraction may be sending a message to the head end 102 (or other serviceprovider device) for software instruction reloading to the STB. Otherinteractions may include rebooting the STB and/or disabling thedecryption of digital content of the STB. In such case, by having theunfavorable comparison of the stored code version to the code versiondetermined from the digital message, the STB may be operated to protectcontent streamed thereto.

FIG. 14 is a block diagram illustrating further the operations of FIG.13 as enacted in one or more embodiments. With the embodiment of FIG.14, a STB 104, client computer 1204, or other computer computing devicereceives digital data from a head end 102, a server computer 1202, oranother computing device. This digital data 1400 includes encryptedcontent and a multi-stage encrypted code version message. This digitaldata 1400 arrives in a format having a plurality of blocks of encryptedcontent and multiple blocks of combined encrypted content and themulti-stage encrypted code version message. With the example of FIG. 14,the digital data 1400 includes encrypted content occupying blocks 0 and1 of the incoming data set and encrypted content and portions of themulti-stage encrypted code version message occupying respective portionsof blocks 2 and 3.

The digital data 1400 is processed by a security processor or otherlogic of the STB 104, client computer 1204, or other computing device,which receives the digital data 1400. With this processing, the securityprocessor or other logic performs first stage decryption operations onthe digital data using a first decryption technique, e.g., AES-CBC, toproduce first decrypted data 1402. In other embodiments, the firstdecryption technique may be another type of decryption technique. Thefirst decrypted data 1402 includes decrypted content and the encryptedcode version message. With the construct of the first decrypted data1402, some decrypted content resides in 128 bit (or byte) blocks. Theseblocks of decrypted content may be suitable for processing. Alternately,this decrypted content may require further processing. The encryptedcode version message spans 128 bit (or byte) blocks such that portionsof the encrypted code version message shares 128 bit (or byte) blockswith decrypted content.

The security processor or other logic then performs section stagedecryption of the encrypted code version message to produce the codeversion message 1404. The security processor may perform furtherverification of the code version message, such as was previouslydescribed with reference to FIGS. 3 and 4. After verification/validationof the code version message, the security processor or other logic maythen compare a stored code version to a reference code version extractedfrom the code version message.

The terms “circuit” and “circuitry” as used herein may refer to anindependent circuit or to a portion of a multifunctional circuit thatperforms multiple underlying functions. For example, depending on theembodiment, processing circuitry may be implemented as a single chipprocessor or as a plurality of processing chips. Likewise, a firstcircuit and a second circuit may be combined in one embodiment into asingle circuit or, in another embodiment, operate independently perhapsin separate chips. The term “chip”, as used herein, refers to anintegrated circuit. Circuits and circuitry may comprise general orspecific purpose hardware, or may comprise such hardware and associatedsoftware such as firmware or object code.

As one of ordinary skill in the art will appreciate, the terms “operablycoupled” and “communicatively coupled,” as may be used herein, includedirect coupling and indirect coupling via another component, element,circuit, or module where, for indirect coupling, the interveningcomponent, element, circuit, or module does not modify the informationof a signal but may adjust its current level, voltage level, and/orpower level. As one of ordinary skill in the art will also appreciate,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two elementsin the same manner as “operably coupled” and “communicatively coupled.”

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention.

One of average skill in the art will also recognize that the functionalbuilding blocks, and other illustrative blocks, modules and componentsherein, can be implemented as illustrated or by discrete components,application specific integrated circuits, processors executingappropriate software and the like or any combination thereof.

Moreover, although described in detail for purposes of clarity andunderstanding by way of the aforementioned embodiments, the presentinvention is not limited to such embodiments. It will be obvious to oneof average skill in the art that various changes and modifications maybe practiced within the spirit and scope of the invention, as limitedonly by the scope of the appended claims.

The invention claimed is:
 1. An apparatus comprising: a communication interface configured to receive a digital message and digital content; memory configured to store the digital message and the digital content; a transcoder coupled to the memory, the transcoder configured to perform transcoding of the digital content, the transcoding including operations involving the digital content in a non-scrambled format; a central processing unit coupled to the communication interface, to the memory, and to the transcoder; and a security processing circuitry coupled to the communication interface, to the memory, and to the transcoder, the security processing circuitry configured to: extract a rights portion from the digital message; decrypt the rights portion; based upon the decrypted rights portion, identify protected digital content of the digital content that is to be isolated from the central processing unit during transcoding by the transcoder; and isolate non-scrambled protected digital content from the central processing unit disposed within the apparatus during the transcoding of the protected digital content by the transcoder.
 2. The apparatus of claim 1, wherein in isolating the non-scrambled protected digital content from the central processing unit during the transcoding the security processing circuitry is configured to: determine a protected portion of the memory in which the transcoder is configured to store non-scrambled protected digital content during the transcoding; and preclude access by the central processing unit to the protected portion of the memory during the transcoding.
 3. The apparatus of claim 2, wherein the protected portion of the memory comprises buffer memory accessible by the transcoder and not accessible by the central processing unit.
 4. The apparatus of claim 1, wherein in identifying protected digital content of the digital content that is to be isolated from the central processing unit during transcoding, the processing circuitry is further configured to identify the protected digital content using a key portion of the digital message.
 5. The apparatus of claim 4, wherein in identifying the protected digital content from the digital message, the security processing circuitry is configured to: extract the key portion from the digital message; and decrypt the key portion.
 6. The apparatus of claim 5, wherein: the decrypted key portion comprises a plurality of content identifiers; and the decrypted rights portion comprises protection data for each of the content identifiers.
 7. The apparatus of claim 5, wherein in extracting the rights portion from the digital message the security processing circuitry is configured to: decrypt a key portion to produce a decrypted result; and decrypt the rights portion using the decrypted result to produce the decrypted rights portion.
 8. The apparatus of claim 5, wherein: the rights portion further comprises a validation portion; and the security processing circuitry is further configured to validate the validation portion.
 9. The apparatus of claim 1, wherein: a protected portion of the memory is inaccessible to the central processing unit during the transcoding; and the security processor directs the transcoder to store the digital content in the protected portion of the memory when in a non-scrambled format.
 10. The apparatus of claim 1, wherein the apparatus comprises at least one of: a cable set top box receiver; a satellite set top box receiver; a Digital Subscriber Line (DSL) set top box receiver; a Wireless Wide Area Network (WWAN) receiver; a client computer; a tablet computing device; or a phone.
 11. The apparatus of claim 1, wherein the security processor is configured to isolate both the transcoder input and the transcoder output from the central processing unit.
 12. The apparatus of claim 1, wherein the security processor is configured to isolate at least some of a plurality of buffers of the transcoder from the central processing unit during transcoding.
 13. The apparatus of claim 1, wherein the security processor is configured to cause the transcoder to use memory having particular addresses for storage of intermediate content during transcoding.
 14. The apparatus of claim 1, wherein the security processor is configured to limit access of the central processor to buffers used by the transcoder for storage of intermediate transcoding content.
 15. The apparatus of claim 1, further comprising a Direct Memory Access (DMA) engine configured to encrypt transcoder output before the output is transferred from a protected portion of the memory.
 16. A method comprising: receiving a digital message and digital content; storing the digital message and the digital content in memory; extract a rights portion from the digital message; decrypt the rights portion; utilizing the decrypted rights portion to identify protected digital content of the digital content that is to be isolated from the central processing unit during transcoding; retrieving the digital content from memory; transcoding the digital content, including transcodinq operations involving a non-scrambled version of the protected digital content; and during the transcoding, isolating the protected digital content from a central processing unit disposed within the apparatus.
 17. The method of claim 16, wherein isolating the protected digital content from the central processing unit during the transcoding comprises: determining a protected portion of the memory in which a transcoder is configured to store non-scrambled protected digital content during the transcoding; and precluding access by the central processing unit to the protected portion of the memory during the transcoding.
 18. The method of claim 16, wherein utilizing the decrypted rights portion to identify protected digital content of the digital content that is to be isolated from the central processing unit during transcoding further comprises identifying the protected digital content using a key portion of the digital message.
 19. The method of claim 18, wherein identifying the protected digital content from the digital message comprises: extracting the key portion from the digital message; and decrypting the key portion.
 20. The method of claim 19, wherein: the decrypted key portion comprises a plurality of content identifiers; and the decrypted rights portion comprises protection data for each of the content identifiers.
 21. The method of claim 19, wherein extracting the rights portion from the digital message comprises: decrypting a key portion to produce a decrypted result; and decrypting the rights portion using the decrypted result to produce the decrypted rights portion.
 22. The method of claim 20: wherein the rights portion further comprises a validation portion; and further comprising validating the validation portion.
 23. The method of claim 16, further comprising: isolating a protected portion of the memory from the central processing unit during the transcoding; and storing the digital content in the protected portion of the memory when the digital content is in a non-scrambled format.
 24. The method of claim 16, further comprising isolating both the transcoder input and the transcoder output from the central processing unit.
 25. The method of claim 16, further comprising isolating at least some of a plurality of buffers of a transcoder from the central processing unit during transcoding.
 26. The method of claim 16, further comprising causing a transcoder to use memory having particular addresses for storage of intermediate content when transcoding the digital content.
 27. The method of claim 16, further comprising limiting access of the central processor to buffers used by a transcoder for storage of intermediate transcoding content when transcoding the digital content.
 28. The method of claim 16, further comprising encrypting the transcoded digital content before the transcoded digital content is output from a protected portion of memory.
 29. A method comprising: receiving a digital message and digital content by a Set Top Box (STB) from a head end, the digital content in a scrambled format; identifying protected digital content of the digital content that is to be isolated from a central processing unit of the STB during transcoding by: extracting a key portion from the digital message; decrypting the key portion; extracting a rights portion from the digital message; decrypting the rights portion based on the decrypted key portion; and identifying the protected digital content based upon the rights portion; and transcoding the digital content, including descrambling the protected digital content and isolating the protected digital content from the central processing unit during the transcoding.
 30. The method of claim 29, wherein isolating the protected digital content from the central processing unit during the transcoding comprises: extracting a code version from the rights portion and comparing the code version to a stored code version to determine whether the code version is valid; storing the digital content in a protected portion of memory when in a non-scrambled format; and isolating the protected portion of the memory from the central processing unit during the transcoding. 